Cutting tools have been used in both coated and uncoated conditions for machining metals and alloys. In order to increase cutting tool wear resistance and lifetime, one or more layers of refractory materials have been applied to cutting tool surfaces. TiC, TiCN, TiOCN, TiN and Al2O3, for example, have been applied to cemented carbide substrates by CVD.
Further, cutting tools based on polycrystalline cubic boron nitride (PcBN) substrates continue to gain importance in the metal working industry given the high hardness and thermal stability (up to about 980° C.) of cBN. Similar to cemented carbides, cutting tools based on PcBN substrates can also benefit from the application of refractory coatings for various cutting applications including, machining of case-hardened and through-hardened steels, superalloys and cast iron. However, while being generally effective for inhibiting wear and extending PcBN tool life, refractory coatings have struggled in applications involving materials having poor machinability, such as unaged cast iron.